SYNTHESIS OF VANADIUM PHOSPHORUS OXIDE CATALYSTS BY AEROSOL PROCESSING

The use of an aerosol process to prepare vanadium phosphorus oxide (VP O) catalysts for butane oxidation to maleic anhydride was investigated . Heating an aerosol created with air of an aqueous solution of NH4VO3 and H3PO4 with phosphorus to vanadium atomic ratio P/V = 1.2 at 700 d egrees C resulted ina material that had an average vanadium oxidation state of 4.7-5.0. After activation in a butane and oxygen mixture, a s table catalyst was obtained which showed selectivities to maleic anhyd ride (MA) of up to 48% at 475 degrees C. X-ray diffraction and laser R aman spectroscopic characterization of the catalyst showed that the as -prepared sample was mostly VOPO4 . 2H(2)O, which was converted to alp ha(I)-VOPO4 under reaction conditions. The catalyst was much more acti ve than a VPO catalyst with P/V = 1.1 or 1.2 prepared by the conventio nal method in an aqueous medium. Thus, in spite of its lower surface a rea and selectivity for MA, it produced a higher yield of MA even on t he basis of the weight of catalyst.